Differential diagnosis and prognosis of delayed neuropsychiatric sequelae after acute carbon monoxide poisoning in a patient with schizophrenia: A case report.

Background: Delayed neuropsychiatric sequelae (DNS) is a syndrome that appears days to weeks after acute carbon monoxide (CO) poisoning. DNS shows various neuropsychiatric symptoms, such as mental deterioration and parkinsonism.

Case presentation: Our case was a 37-year-old male with schizophrenia. He attempted suicide by CO poisoning and was brought to our emergency department (Day 0). He was ventilated with normobaric oxygen therapy for 3 days and moved to the psychiatric ward with clear consciousness. We restarted antipsychotics, and he gradually presented akinesia and rigidity. Additionally, around Day 32, he showed disorganized behaviors, mental deterioration, incontinence, and gait disturbance. Brain magnetic resonance imaging (MRI) showed slightly abnormal findings on Day 35. Although we suspected DNS on the clinical course and the MRI findings, catatonia and side-effects of antipsychotics were also considered. Finally, electroencephalography (EEG) on Day 38 with apparent abnormalities, including diffuse slow waves, resulted in our diagnosis of DNS, and he underwent hyperbaric oxygen therapy. His condition was dramatically improved, and his diffuse slow waves on EEG disappeared on Day 83. We also followed his clinical presentations and brain MRI until 33 months. Throughout the whole follow-up, his cognition, movement, and psychiatric symptoms remained stable. However, his brain MRI showed progressive atrophy in bilateral frontal lobes and increasing white matter lesions throughout the whole course.

Conclusion: EEG, as well as brain MRI, may be crucial in the differential diagnosis of DNS in patients with complex conditions involving medications and severe mental illnesses.